Despite many reports of cocaine's ill effects on the developing fetus, scientists lack
definitive evidence specifically linking cocaine to adverse reproductive effects (SN:
9/7/91, p.152). Using a powerful statistical technique, a Canadian research team has found
that cocaine by itself causes very few problems during pregnancy.

Gideon Koren of the University of Toronto and his colleagues identified 20 previously
published cocaine studies that in- volved pregnant women and yielded mixed results. Those
studies often relied on small samples of cocaine users -- a problem that limited each
study's statistical power.

To home in on cocaine's reproductive risks, his team turned to a method called
meta-analysis, which statisticians use to assess data by pooling a number of similar
studies. Koren and his colleagues identified women in the 20 studies who used cocaine
during pregnancy but did not use other illicit drugs or alcohol, and compared them with
those who reported no drug or alcohol use during pregnancy. They found no statistical link
between prenatal cocaine use and premature delivery, low birthweight or congenital heart
defects in babies -- problems often thought to result from cocaine.

The meta-analysis suggests that confounding factors -- such as other drugs, alcohol and
smoking -- may account for the fetal growth retardation or prematurity commonly ascribed
to cocaine, the researchers assert in the October _TERATOLOGY_.

Koren says women who use cocaine tend to smoke more cigarettes than women who use other
illicit drugs and are more likely to drink alcohol and take additional drugs.

The meta-analysis did reveal a chance that a pregnant woman's cocaine use by itself
might cause malformations of the genito-urinary tract in a small number of infants. Koren
says this effect may trace to cocaine-induced constriction of the placental blood vessels.